Fan convector heating unit

ABSTRACT

A fan convector heating unit ( 10 ) has a housing ( 11 ) having an air duct ( 12 ) extending therethrough. A heat exchanger ( 21 ) is disposed within the air duct ( 12 ) and is adapted for fluid connection to a water heating system, when the heating unit ( 10 ) is installed. A fan ( 18 ) is disposed within the housing ( 11 ) and is arranged to cause air to flow through the air duct ( 12 ) and over the heat exchanger ( 21 ). Control means are provided to activate and deactivate the fan ( 18 ) upon the water within the heat exchanger ( 21 ) reaching pre-determined activation and deactivation temperatures. Both the activation and deactivation temperatures are interchangeably variable between standard and low energy activation and deactivation temperatures. Switching means ( 16 ), in communication with the control means, are provided to enable variation between a standard operating mode in which the standard activation and deactivation temperatures are employed, and a low energy operating mode in which the low energy activation and deactivation temperatures are employed.

This invention relates to a fan convector heating unit. In particular, the invention relates to an improved fan convector heater unit having enhanced environmental performance properties.

Conventional fan convector heating units, also referred to as wall-mounting fan convectors or fan-assisted radiators, consist of a heat exchanger fed by the central heating or hot water system of a building in which the fan convector is installed, and an electric fan arranged to blow air over the heat exchanger. Operation of the fan is generally controlled by a built-in thermostatic switch responsive to room temperature changes.

Fan convectors of this construction have been known for many years and enjoyed considerable popularity in the late 1970s. At that time, fan convectors were preferred by many to conventional radiators, due mainly to two considerations: firstly, the forced convection of fan convectors enabled a greater heat output to be ‘harvested’ from the heating system than was the case with radiators, which relied on natural convection currents—and as a consequence of this, a fan convector could be made considerably smaller than a radiator with an equivalent heat output; and secondly, the provision of a room thermostat on fan convectors enabled greater control of individual heating units than was possible with radiators, allowing heating units in different rooms to be operated at different heat outputs.

However, the production and design of conventional radiators developed over the years, with the introduction of high convection fins and double panels to increase the surface area, meaning that the overall space taken up by a radiator could be substantially reduced for any given heat output. Additionally, the development and introduction of thermostatic radiator valves enabled the control of individual radiators in different rooms to achieve the same degree of flexibility as had previously been available only for fan convectors. As a result, fan convectors fell out of fashion for a number of years.

Despite the dominance of radiators over the intervening decades, conventional radiators suffer from one particular shortcoming: because of their reliance on natural convection, they cannot efficiently transfer heat from a building's water heating system to a room when the water in the system is at a low temperature—which in this sense means a temperature below about 75° C. The central heating boiler must therefore be operated at a temperature higher than 75° C., which leads to increased running costs, decreased efficiency, and a greater drain on fuel resources. A further consequence of the high operating temperature of conventional radiators is that they present a potential injury hazard making them unsuitable for use in environments such as schools, hospitals, nursing homes and the like.

In recent years, there has been a marked shift in the behaviour of consumers, who are ever more seeking environmentally benign products and services. Domestic heating is one area in particular in which consumers are seeking to minimise their ‘carbon footprint’, i.e. the impact which their activities have on the earth's resources. This has led many consumers to seek to replace or supplement standard domestic heating fuel sources such as gas and oil with renewable energy sources such as solar, wind or geothermal energy.

However, such renewable sources require large installations in order to produce significant amounts of power such as would be require to heat water in a domestic heating system to a temperature of 75° C., so that the water can be used for room heating via conventional radiators. For most domestic users, such large scale installations are impractical, and so the power generated by renewable sources is generally limited to providing hot water for bathing and washing, at around 45° C., rather than for space heating purposes. Conventional radiators cannot operate efficiently at such low water temperatures.

The present invention seeks to address the above issue by providing a fan convector heating unit capable of operating both at standard operating temperatures such that the unit is operable with water heated by conventional energy sources, and at low energy operating temperatures such that the unit is operable with water heated by renewable energy sources. The present invention further seeks to provide such a heating unit presenting a low temperature on its forward facing external surface, thus rendering the unit safe for use in schools, hospitals, nursing homes and the like.

According to the present invention there is provided a heating unit comprising:

-   -   a housing having an air duct extending therethrough;     -   a heat exchanger disposed within the air duct and adapted for         fluid connection to a water heating system, when installed;     -   a fan disposed within the housing and arranged to cause air to         flow through the air duct and over the heat exchanger;     -   first control means adapted to activate the fan upon the water         within the heat exchanger reaching a pre-determined activation         temperature selected from, and interchangeably variable between,         a standard activation temperature and a low energy activation         temperature;     -   second control means adapted to deactivate the fan upon water         within the heat exchanger falling below a pre-determined         deactivation temperature selected from, and interchangeably         variable between, a standard deactivation temperature and a low         energy deactivation temperature; and

switching means in communication with said first and second control means, and adapted to enable variation between a standard operating mode in which said standard activation and deactivation temperatures are employed, and a low energy operating mode in which said low energy activation and deactivation temperatures are employed.

The standard activation temperature is preferably in the range of from 55° C. to 65° C., and most preferably is around 60° C. The standard deactivation temperature is preferably in the range of from 45° C. to 55° C., and most preferably is around 50° C.

The low energy activation temperature is preferably in the range of from 30° C. to 40° C., and more preferably is around 35° C. The low energy deactivation temperature is preferably in the range of from 28° C. to 34° C., and more preferably is around 31° C.; provided that said low energy deactivation temperature is always at least 2° C. lower than said low energy activation temperature.

In preferred embodiments of the present invention, the heating unit is further provided with a room thermostat in communication with said first and/or second control means. The room thermostat provides the capability to make the activation and deactivation of the fan dependent upon the air temperature of the room in which the heating unit is situated.

The heating unit of the present invention is preferably adapted for mounting on a wall. The housing of the unit preferably comprises at least one panel, adapted to provide a forward facing surface, when the unit is mounted on a wall.

In a preferred embodiment of heating unit according to the present invention, the air duct extends from an inlet grille located at the top of the housing to an outlet grille located at the bottom of the housing, when said unit is mounted on a wall. Ambient air is thus drawn in through the top of the unit, heated within the unit, and the hot air then expelled through the bottom of the unit.

The location of the outlet grille at the bottom of the unit serves two purposes. Firstly, as will be described in more detail below, the outlet grille is the only external part of the unit which becomes hot during use. Locating the outlet grille at the bottom the unit therefore ensures that the grille is not readily accessible, thus substantially reducing the risk of injury. Secondly, the emission of heated air from the bottom, rather than the top, of the unit means that the heated air gently drifts across the floor of the room, thus eliminating the cold drafts often associated with other heat emitting apparatus.

In a preferred construction of heating unit according to the present invention, the heat exchanger is located adjacent the outlet grille, whilst the air duct preferably further comprises a plenum chamber located between the inlet and outlet grilles. In such embodiments, the fan is preferably disposed in the air duct between the inlet grille and the plenum chamber, thereby to draw air through the inlet grille and drive it into the plenum chamber. Most preferably, the heat exchanger is located in the plenum chamber.

The housing preferably comprises at least one panel isolated from the plenum chamber such that an external surface of said at least one panel remains at ambient temperature when the unit is in operation. Most preferably, said at least one panel of the housing isolated from the plenum chamber includes a panel adapted to be forward facing when the unit is mounted on a wall. This may conveniently be achieved by locating said forward facing panel adjacent a first portion of the air duct channeling only ambient air. Preferably therefore, a first portion of the air duct extending from the inlet grille to the fan is disposed adjacent said forward facing panel. Most preferably, only said first portion of the air duct is disposed adjacent said forward facing panel—that is to say, the forward facing panel is isolated from any portion(s) of the air duct channeling heated air. The or each panel of the housing is preferably also isolated from the heat exchanger.

The above described construction enables ambient air to be drawn down through the inlet grille and down the first portion of the air duct adjacent the forward facing panel, thus keeping said panel cool. The heating of the air by the heat exchanger occurs within the plenum chamber—and the forward facing panel is isolated from both the heat exchanger and the plenum chamber. The forward facing panel therefore remains cool at all times, thus substantially reducing or eliminating the risk of injury.

The fan is preferably a tangential fan. The heat exchanger is preferably a high efficiency slit finned heat exchange, and most preferably has a fin density of substantially 4 fins per cm (10 fins per inch, fpi). The use of a tangential fan in combination with a high efficiency 10 fpi slit finned heat exchanger is thought to increase heat transfer by up to 20% over conventional heat exchangers.

The housing may desirably be shaped and/or styled to give the appearance of a conventional radiator heating unit. Additionally, or alternatively, the housing may be painted or otherwise decorated to blend in with the décor of the room in which the heating unit is located.

In order that the present invention may be better understood, a preferred embodiment thereof will now be described, though only by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows a front perspective view of a fan convector heating unit according to the present invention;

FIG. 2 shows a front view of the fan convector heating unit of FIG. 1, with the front panel removed; and

FIG. 3 shows a cross-sectional side view of the fan convector heating unit of FIG. 1.

Referring first to FIG. 1, there is shown a fan convector heating unit, generally indicated 10, according to the present invention. The heating unit 10 comprises a housing 11 having an air duct 12 (not visible in FIG. 1) extending therethrough from an inlet grille 13 located at the top of the housing 10 to an outlet grille 14 located at the bottom of the housing 11.

The housing 11 features a front panel 15 defining one wall of a first portion 17 of the air duct 12. As will be described in more detail below with reference to FIG. 3, the components of the heating unit 10 are arranged such that the front panel 15 defines a wall of the air duct 12 only over said first portion 17 through which ambient air is channeled, the panel 15 being isolated from all heated components of the unit 10. This enables the panel 15 to remain at ambient temperature when the unit 10 is in operation, thus effectively eliminating any risk of burn injuries, and so making the unit 10 suitable for use in schools, hospitals, nursing homes and the like.

At the top of the housing 11 is located a control panel 16. The control panel 16 provides a facility for a user to switch the operating mode of the unit 10 between a standard operating mode and a low energy operating mode, as hereinbefore described.

Referring now to FIG. 2, this shows the fan convector heating unit 10 of FIG. 1, with the front panel 15 removed to reveal the internal components of the unit 10. A tangential fan 18 is mounted in the air duct 12, and is arranged to blow air into a plenum chamber 19 within which is located a high efficiency heat exchanger 21 connected to a domestic water heating system (not shown).

The operation of the fan convector heating unit 10 according to the present invention will now be described with reference to FIG. 3.

First, the operating mode for the fan convector heating unit 10 is selected using the control panel 16. The control panel 16 enables the user to switch between a standard operating mode and a low energy operating mode. In standard operating mode, the tangential fan 18 is automatically activated upon water within the heat exchanger 21 reaching a standard activation temperature of substantially 60° C., and is automatically deactivated upon water within the heat exchanger 21 falling below a standard deactivation temperature of substantially 50° C. In low energy operating mode, the fan 18 is automatically activated upon water within the heat exchanger 21 reaching a low energy activation temperature of substantially 35° C., and is automatically deactivated upon water within the heat exchanger 21 falling below a low energy deactivation temperature of substantially 31° C. The activation and deactivation of the fan 18 is controlled, respectively, by first and second control means (not shown) in communication with the control panel 16.

Upon water in the heat exchanger 21 reaching the activation temperature appropriate to the selected operating mode, the fan 18 is activated, causing ambient air to be drawn in through the inlet grille 13 at the top of the housing 11, as indicated by arrows a. The ambient air is then drawn down through a first portion 17 of the air duct 12 defined between the front panel 15 and the fan 18, as indicated by arrows b, before being drawn into and through the tangential fan 18, as indicated by arrows c. Here, the air stream is accelerated and driven into the plenum chamber 19, as indicated by arrows d. It should be noted that, the air stream passing through the first portion 17 of the air duct 12 between the front panel 15 and the fan 18, remains at ambient temperature, only being heated when it reaches the plenum chamber 19. The front panel 15 is therefore always in contact with ambient air in the first portion 17 of the air duct 12, and is isolated from the plenum chamber 19, thus ensuring that the external surface of the front panel 15 always remains cool to the touch, effectively eliminating the risk of burn injuries.

Once inside the plenum chamber 19, the air stream is driven over, around and through the coils and fins (not shown) of the high efficiency heat exchanger 21, as indicated by arrows e, causing the air to be heated. The heated air stream then exits the fan convector heating unit 10 via the outlet grille 14 located at the bottom of the housing 11, as indicated by arrow f. 

1. A heating unit comprising: a housing having an air duct extending therethrough; a heat exchanger disposed within the air duct and having connectors for fluid connection to a water heating system, when installed; a fan disposed within the housing and arranged to cause air to flow through the air duct and over the heat exchanger; a first control for activating the fan upon the water within the heat exchanger reaching a pre-determined activation temperature selected from, and interchangeably variable between, a standard activation temperature and a low energy activation temperature; a second control for deactivating the fan upon water within the heat exchanger falling below a pre-determined deactivation temperature selected from, and interchangeably variable between, a standard deactivation temperature and a low energy deactivation temperature; and a switch in communication with said first control and said second control, said switch enabling variation between a standard operating mode in which said standard activation and deactivation temperatures are employed, and a low energy operating mode in which said low energy activation and deactivation temperatures are employed.
 2. The heating unit as claimed in claim 1, wherein the standard activation temperature is in the range of from 55° C. to 65° C. and the standard deactivation temperature is in the range of from 45° C. to 55° C.
 3. The heating unit as claimed in claim 1, wherein the standard activation temperature is substantially 60° C., and the standard deactivation temperature is substantially 50° C.
 4. The heating unit as claimed in claim 1, wherein the low energy activation temperature is in the range of from 30° C. to 40° C. and the low energy deactivation temperature is in the range of from 28° C. to 34° C.; provided that said low energy deactivation temperature is always at least 2° C. lower than said low energy activation temperature.
 5. The heating unit as claimed in claim 1, wherein the low energy activation temperature is substantially 35° C. and the low energy deactivation temperature is substantially 31° C.
 6. The heating unit as claimed in claim 1, further comprising a room thermostat in communication with at least one of the first control and the second control means.
 7. (canceled)
 8. The heating unit as claimed in claim 1, wherein said heating unit is mountable on a wall, and wherein the air duct extends from an inlet grille located at the top of the housing to an outlet grille located at the bottom of the housing, when said unit is mounted on a wall.
 9. The heating unit as claimed in claim 8, wherein the heat exchanger is located adjacent the outlet grille.
 10. The heating unit as claimed in claim 8, wherein the air duct further comprises a plenum chamber located between said inlet and outlet grilles.
 11. The heating unit as claimed in claim 10, wherein the fan is disposed in the air duct between the inlet grille and the plenum chamber, thereby to draw air through the inlet grille and drive said air into the plenum chamber.
 12. The heating unit as claimed in claim 11 wherein the heat exchanger is located in the plenum chamber.
 13. The heating unit as claimed in claim 12, wherein the housing comprises at least one panel isolated from the plenum chamber such that an external surface of said at least one panel remains at ambient temperature when the unit is in operation.
 14. The heating unit as claimed in claim 13, wherein said at least one panel of the housing isolated from the plenum chamber includes a panel adapted to be forward facing when the unit is mounted on a wall.
 15. The heating unit as claimed in claim 14, wherein a first portion of the air duct extending from the inlet grille to the fan is disposed adjacent said forward facing panel.
 16. (canceled)
 17. The heating unit as claimed in claim 14, wherein the outlet grille is angled relative to said forward facing panel.
 18. The heating unit as claimed in claim 12, wherein each panel of the housing is isolated from the heat exchanger.
 19. The heating unit as claimed in claim 1 wherein the fan is a tangential fan.
 20. The heating unit as claimed in claim 1, wherein the heat exchanger is a high efficiency slit finned heat exchanger.
 21. The heating unit as claimed in claim 20, wherein the heat exchanger has a fin density of substantially 4 fins per cm.
 22. The heating unit as claimed in claim 1, wherein the housing is shaped and styled to give the appearance of a conventional radiator heating unit. 